What is the internal diameter of the fetal colon?

When a woman first becomes pregnant, the fertilized egg just implants in the uterus. Then during the long pregnancy, the fertilized egg will begin a series of complex development processes. This process is very magical. In the middle and late stages of pregnancy, the fetus will become larger and have more organs and functions. So, under normal circumstances, what is the inner diameter of the fetus's colon?

What is the internal diameter of the fetal colon?

My wife is in the late stage of pregnancy, and ultrasound examination showed that the width of the intestine had increased, but was less than 25 mm. This situation may also be caused by the baby's feces. It is recommended not to worry, as this situation may be a physiological phenomenon. The ultrasound can be repeated in two weeks. Abdominal pain occurs, which is a sign of irregular uterine contractions and can usually be relieved by rest.

To establish the normal reference range of fetal colon diameter in late pregnancy. Methods: 193 healthy pregnant women with normal singleton gestation at 36-40+3 weeks were enrolled. The maximum inner diameter of the fetal colon at each gestational week was measured using real-time color ultrasound. Results: The normal mean values ​​and upper limits of 95% confidence intervals of fetal colon diameter at 36-36+6 weeks, 37-37+6 weeks, 38-38+6 weeks, 39-39+6 weeks and ≥40 weeks were (11.03±2.19) mm, (13.27±1.84) mm, (14.94±2.40) mm, (16.22±2.01) mm and (17.26±3.68) mm and 15.8 mm, 16.24 mm, 18.57 mm, 19.24 mm and 22.92 mm, respectively. Conclusion: The normal range of fetal colon diameter at each gestational week in late pregnancy is provided, which can be used as a reference value for evaluating the intrauterine development of the colon and detecting abnormalities in the development of the fetal intestinal tract.

This symptom is difficult to distinguish between the fetal jejunum and ileum by ultrasound. High-resolution ultrasound can distinguish between the fetal intestine and other structures in the abdomen. Prenatal ultrasound examination found multiple echo-free intestinal sections in the mid-abdomen of the fetus and they persisted. The possibility of small intestinal atresia should be suspected, but the exact location, type and cause of the atresia cannot be displayed and determined by prenatal ultrasound. Small intestinal atresia can usually be detected in the late pregnancy after 24 weeks. When the inner diameter of the small intestine is greater than 7mm, it indicates that there may be small intestinal obstruction; the dilated intestinal tube is located in the mid-abdomen of the fetus, showing multiple echo-free areas; multiple ultrasound examinations show that the diameter of the small intestine is progressively enlarged. Real-time ultrasound observation shows that the small intestinal peristalsis is significantly enhanced, which can clearly show intestinal peristalsis and reverse peristalsis; it may be accompanied by signs of fetal intra-abdominal calcification, fetal ascites or excessive amniotic fluid. Pay attention to differentiation from large intestine dilatation, ureteral dilatation, and intra-abdominal cysts.

Colonic atresia may manifest as colonic dilatation. In some cases, there may be no obvious colonic dilatation. The diameter of the large intestine increases with the increase of gestational age. Whether the colon is dilated should be judged according to the gestational age at the time of examination. Colonic dilatation may be a transient manifestation. Therefore, if colonic dilatation is found, it is necessary to recheck several times to observe the width of the colon and whether it is progressively dilated to determine whether it is physiological or pathological dilatation. The diameter of the colon of a normal fetus does not exceed 7mm at 25 weeks and does not exceed 18mm at full term. If the transverse diameter of the large intestine is greater than 20mm in late pregnancy, intestinal obstruction should be suspected. In case of anal atresia, a cystic mass with a bilobed sign is often shown in the lower part of the fetal pelvis. If intestinal dilatation is not found, the possibility of anal atresia cannot be ruled out. Ultrasound diagnosis of anal atresia lacks specificity. When anal atresia is combined with rectourethral fistula, prenatal ultrasound can show multiple strong echogenic light groups in the dilated intestinal tube. In late pregnancy, the echo of the dilated colon is seen, and the amount of amniotic fluid is often normal.

Congenital Hirschsprung's disease is characterized by intestinal dilatation. Ultrasound is not specific, and it is difficult to determine whether the intestinal dilatation is caused by congenital Hirschsprung's disease or other reasons. Prenatal ultrasound is difficult to make an accurate diagnosis of this disease.